Metal ladder



Oct. 7, 1958 Filed Oct. 4, 1956 i sa ll H. G. ARNOLD 2,855,134

METAL LADDER 2 Sl'xeecs-Slnee'fl 1 4 INVENTOR. /5 HH/FL 57952170527 www@@uw oct. 7, 195s 2,855,134

H. G. ARNOLD METAL LADDER Filed Oct. 4, 1956 2 Sheets-Sheecl 2 Ffa-5 lFfa-7 INVENTOR.

ilnite Patent C) METAL LADDER Harold G. Arnold, Wooster, Ohio, assignorto Bauer Manufacturing Company, Wooster, Ohio, a corporation of OhioApplication October 4, 1956, Serial No. 614,004

3 Claims. (Cl. 228-56) This invention relates Ito metal ladders, andmore particularly, is concerned with an improved sheet metal laddercharacterized by high strength and light weight.

Various types of metal ladders have been proposed heretofore, and somehave been made and sold, but these have usually been made from extrudedaluminum or aluminum alloy sections which are often relatively heavy inorder to provide the requisite strength. Efforts to make a metal ladderfrom steel have not been very satisfactory for the reason that theresulting ladders have always been objectionably heavy, and subject tocorrosion. Additionally, for many industrial uses of ladders aroundelectric wiring, steam pipes, and the like, wooden ladders have beenpreferred because of their non-electrical conductivity.

It is the general object of my invention to avoid the foregoing andother objections to and difliculties of prior art practices by theprovision of an improved relatively light-weight but high strengthladder made from sheet steel.

Another object of my invention is the provision of a sheet metalload-carrying member for a ladder, the sheet metal being rolled toprovide substantially tubular columns along its edges and with the edgesof the strip overlapping and being welded to each other and to thecenter or base portion of the strip.

Another object of my invention is the provision of a metal ladderprotected against corrosion and electric conductivity by a tough durablecoating layer of plastic covering substantially the entire outer surfaceof the ladder.

Another object of my invention is the provision of a metal ladder havingthe simplicity of fabrication and the high strength of steel, butapproaching the lighter weight of aluminum and its alloys or of wood.

Another object of my invention is the provision of a metal laddercharacterized by relatively low initial and maintenance cost, greatdurability, and simplicity of manufacture.

A still further object is to provide a metal ladder having tubular rungsof triangular cross-section having treads inclined to the standards andhorizontal in an inclined ladder.

The foregoing objects of my invention, and other objects which willbecome apparent as the description proceeds, are achieved by theprovision of a ladder having standards each comprising a strip of sheetmetal having its edges bent to form substantially tubular columns andwith the edges of the strip continuing into overlapping relation witheach other and in substantial engagement with the center of the strip,means welding the overlapping edges to each other and to the centerportion of the strip,l sheet metal rungs having integral flanges ontheir ends, means welding the rung flanges to the inwardly turnedoverlapping edges of the strip of sheet metal and to the center portionof the strip of sheet metal forming each standard. Usually sheet metalcaps are provided over the ends of the standards, and I preferably iceprovide a tough durable coating of plastic over substantially the entireouter surface of the ladder to render the ladder non-conductive ofelectricity, and to protect it against corrosion.

For a better understanding of my invention, reference should be had tothe accompanying drawings wherein:

Fig. l is a front view of a ladder constructed in accord with theprinciples of my invention, certain portions thereof being broken awayand others shown in section;

Fig. 2 is a cross-sectional view taken substantially on line II-II ofFig. l;

Fig. 3 is a cross-sectional view taken substantially on on line III-IIIof Fig. l;

Fig. 4 is a cross-sectional View taken substantially on line IV--IV ofFig. 3, but on a reduced scale;

Fig. 5 is a diagrammatic perspective view of a at step-type rung whichmay be used instead of the tubular rung.

Fig. 6 is a front view of a ladder showing a modification of the ladderrung;

Fig. 7 is a cross-sectional view on an enlarged scale, taken on lineVII-VII of Fig. 6.

In the drawings, the numeral 16 indicates generally a pair of uprightsor standards which are joined together at spaced points by rungs 12. Inaccord with the teaching of the invention, each standard 10 is made froma single strip of sheet metal having a base portion 14 terminating insubstantially right angle ilanges 16, the edges of the strip beingcontinued and bent inwardly back towards each other at 17 to form angleX which is equal to at least about to thereby form substantially tubularcolumns 18 along each edge of the strip.

The inwardly turned ends or edges 20 of each sheet metal strip afterdefining the columns 18 are bent to overlap each other in the mannersho-wn in Fig. 2, and with at least one of the edges 20 engaging withthe center portion of the base 14, and with the base 14 and theoverlapped edges 20 being welded together usually by spot-weldspositioned every inch or two along the length of the standards.

It is also possible to seam or line-weld the base 14 to the overlappededges 20, instead of spot-welding them.

The resulting standards made from sheet metal because of the spacedcolumns 18 and the overlapping of the edges 20 and the welding of theseedges to each other and to the center portion of the base 14, results ina very high strength load carrying member, and this is true even thoughthe gauge of the sheet metal is reduced materially below the thicknessof an extruded aluminum alloy section so that the improved load carryingmember of my invention is definitely competitive with aluminum alloyfrom a weight standpoint, and, further, possesses the characteristicthat the sheet metal can be quickly rolled from the at or skelp througha series of stands of rolls into the form illustrated and described,followed by a relatively rapid welding operation so that the manufactureis simple, inexpensive, and rapid.

Figs. 3 and 4 illustrate the positioning and shape of the parts at thepoint of joinder of each rung 12 with the standard 10.

The end of each tubular sheet metal rung 12 is provided with an integralbelled flange 24 which extends at right angles to the rung itself. Inorder to receive the belled ange 24, substantially circular recesses 26are provided in each standard 10 and this is accomplished by flatteningthe inwardly turned flange portions 17 to bring them into substantialalignment with the edges 20 and into substantial engagement with thebase 14, so that spot-welds 28 can be provided at a plurality ofcircumferentially spaced points on the bell ilange 24 to secure theflange 24 to the base 14 and the flange portion 17.

It is often desirable to cover the ends of the standards 3 10, and asillustrated at the lower left-hand side of Fig. 1, this can beaccomplished by the provision of sheet metal caps 30 which are shaped toslide over the ends of the standards being suitably tack or spot-weldedinto position.

The end of the cap 3:0` may be provided with arubber or other wear-pad32 which is vulcanized or secured to the end of the cap.

An important feature of the invention is the provision of a toughdurable coating layer 34 of plastic over substantially the entire outersurface of the ladder, this being usually applied, to the ladder bydipping the ladder in a liquid bath of Plastic, removal of the ladderfrom the bath and the setting up of the plastic by evaporation ofsolvents and/or the application of heat to effect vulcanization orpolymerization. I typically employ a polyvinyl chloride plastic whichadhesively secures itself to the entire outer surface of the ladder andwhich serves to protect the ladder against corrosion and likewise torender the ladder non-conductive to electricity.

Normally the thickness of the plastic layer 34 is at least equal to thethickness of the sheet metal, but preferably I make the layer abouttwice the thickness of the sheet metal in the manner ratherdiagrammatically shown in the drawings. It should be understood .that inthe drawings, the thickness of the sheet metal and of the plastic hasbeen somewhat exaggerated in order to more clearly illustrate the parts,and that in the actual practice of the invention they sheet metal isnormally not thicker than number 24 gauge, and oft-times thinner gaugesthan number 24 can be employed to achieve the advantages of theinvention.

Fig. illustrates a modification of the rung structure of the ladder ofthe invention, the numeral 36 indicating a llat step-type rung made froma rolled strip of sheet metal contoured substantially in the mannerparticularly illustrated and described with respect to the standards 10,but with the rung 36 being somewhat smaller in width and verticalheight, and with the overlapping edges 38 of the edges of the strip4engaging each other and the center portion of the base of the strip andbeing spotwelded together at longitudinally spaced points 40. A rung ofthis type is provided with integral end flanges which can be spot orotherwise welded to the standards by providing a substantiallyrectangular recess in the standards instead of the circular recess 26.

Figs. 6 and 7 illustrate another modification of the invention in whichthe ladder rungs are tubular and of triangular cross-section with thetread surfaces inclined relative to the standards. In this form of theinvention, the rung 12 is made of sheet metal formed to provide a tubeof triangular cross-'section having a one generally flat face 45inclined to the standards so as to present a horizontal tread face whenthe ladder is inclined as against apbuilding. The other two faces 46, 47brace the tread face and their lower margins are preferably overlappedand welded as at 48. The tread face 45 may be formed with longitudinalcorrugations 49 or other projections to increase resistance to slipping.

The ends of the rungs are formed with outwardly turned llanges 50 whichare welded to the standards.

From the foregoing, it will be recognized that the various objects of myinvention have been achieved by the provision of a simplified,inexpensive, light-weight and durable steel ladder having particularlyhigh strength, and adapted to be covered with plastic to protect theladder against corrosion and to render it non-conductive of electricity.

In accord with the patent statutes, I have specifically illustrated anddescribed one best known embodiment of my invention, but it is to beparticularly understood that I am not to be limited thereto or thereby,but that the scope of my invention is to be defined in the lappendedclaims.

Iclaim:

1. The combination in a ladder of sheet metal standards, each standardbeing made from a single strip of f sheet metal having its edges turnedat substantially right angles to form flanges and the edges of theilanges being turned inwardly at angles of at least about degrees toengage with the center portion of the strip and define therewithlongitudinal spaces triangular in cross-section throughout the standard,the edges overlapping and being flattened to engage with each other andwith the center portion of the strip, means welding the flattened edgesto each other and to the center portion of the strip at close intervalsto provide a three-ply longitudinal reinforcement, rungs of tubularsheet metal, belled integral flanges on the ends of the rungs, andmeansv welding the belled flanges to the inwardly turned edges of thellanges of the standards and .to the reinforced center portion thereof,the inwardly turned edges of the flanges being pressed toward the rightangle flanges in the regions adapted to receive the belled flanges toprovide circular socket-like recesses.

2. The combination in a ladder of sheet metal standards, each standardbeing made from a single strip of sheet metal having its edge-s turnedat substantially right angles toform flanges and the edges of theflanges being turned inwardly to engagev with the center portion of the.strip and to define therewith longitudinal spaces triangular incross-section throughout the standards, the edges overlapping andA beingllattened to engage with each other and with the center portion of thestrip, means welding the flattened edges to each other and to the centerportion of the strip at close intervals to provide a three-plylongitudinal reinforcement, rungs of tubular sheet metal, belledintegral flanges on the ends of the rungs, means welding the belledflanges `to the inwardly turned edges of the flanges of the standardsand to the center portion thereof, and a tough durable coating layer ofplastic covering the entire outer surface of the ladder.

3. The combination in a ladder of sheet metal standards, eachstandardbeing made from a single strip of sheet metal having its edges turned atsubstantially right angles to form ilanges and the edges of the flangesbeing turned inwardly to engage with the center portion of the strip andto define therewith longitudinal spaces triangular in cross-sectionthroughout the standards, the edges overlapping and being flattened toengage with each other and with the center portion of the strip, meanswelding the flattened edges to each other and to the center portion ofthe strip at close intervals to provide a three-ply longitudinalreinforcement, rungs of sheet metal, integral flanges on the ends of therungs, and means Welding the rung flanges to the inwardly turned edgesof the llanges of the standards and to the center portion thereof.

References Cited in the file of this patent UNITED STATES PATENTS670,309 Carnahatn Mar. 19, 1901 975,223 Ferguson Nov. 8, 1910 2,127,035Kirlin Aug. 16, 1938 2,510,515 Myberg June 6, 1950 2,727,672 De LucaDec. 20, 1955 FOREIGN PATENTS 815,433 France Apr. 12, 1937 731,3.77Great Britain June 8, 1955

